Soil-based septic systems serve 20%-25% of the households in the U.S. (U.S. Census Bureau, 2007; U.S. Environmental Protection Agency [U.S. EPA], 2008) and about one million homes in Ohio. This translates to about 480 million gallons of treated effluent per day throughout Ohio (Ohio Department of Health, 2008). In its report to the U.S. Congress, however, the U.S. Environmental Protection Agency (U.S. EPA) stated that onsite septic systems constitute the third most common source of groundwater contamination and that these systems fail due to inappropriate siting, poor design, or inadequate maintenance (U.S. EPA, 1996a). The discharge of partially treated sewage from malfunctioning onsite systems was identified by U.S. EPA as a contributor to excess nutrients in ponds, lakes, and coastal estuaries; contamination of drinking water and groundwater sources; and a cause of several viral and bacterial illnesses through consumption of drinking water contaminated by failing septic systems (U.S. EPA, 1996b, 2000).
In a follow-up report to Congress, U.S. EPA (1997) stated that "adequately managed decentralized wastewater systems are a cost-effective and long-term option for meeting public health and water quality goals, particularly in less densely populated areas." Some communities have successfully utilized onsite systems for wastewater management. Mancl (2002) presented four such success stories from the states of Iowa, Colorado, and California to build the case for adopting onsite systems in rural areas.
The objective of our study was to determine if coordination of laws and regulations, educational programs, and advances in technology can provide homeowners with effective and affordable wastewater treatment systems that protect the public health. To meet this objective, our study worked to deconstruct the formulation of current onsite wastewater treatment policy in Ohio. As of now, Ohio has the oldest sewage rules in the U.S. (Ohio Department of Health, 2008) based on the Ohio Administrative Code (Household Sewage Disposal Systems, 1977).
Materials and Methods
Our study utilized a triangulated inquiry to gather information about the policies governing septic systems in Ohio and the current practices and attitudes of the regulators. Public records of the Ohio legislature and the Ohio Department of Health were primary sources of information. News sources were accessed to verify conflicting information. Further, county health departments in Ohio were surveyed in 2005 about existing practices, attitudes, and educational needs.
The survey questionnaire was prepared using the procedure described by Dillman (1978). The questionnaire booklet consisted of a front cover illustration and seven pages of multiple-choice and fill-in-the-blank questions. Prior to distribution, the questionnaire was tested by three experts to ensure that the questions were clear and appropriate. The complete questionnaire is available in Hacker (2007) and can be obtained from the authors. Following Dillman's technique, the questionnaires were distributed to all 88 counties through a four-part mailing process. The first mailing contained a personally addressed and signed cover letter, the questionnaire booklet, and a preaddressed and stamped return envelope. After two weeks, a reminder postcard was sent to all the counties. Two weeks later a second letter, the questionnaire booklet, and a return envelope were sent to those who did not respond. Finally, two weeks later, a second reminder postcard was sent to the remaining nonrespondents.
Ohio's Septic Systems Regulations
Onsite sewage systems in Ohio are regulated through state law and state rules. Local health districts, however, can adopt more stringent regulations depending on their requirements. Chapter 3718 of the Ohio Revised Code (Sewage Treatments Systems, 2006) and chapter 3701-29 of the Ohio Administrative Code (OAC) (Household Sewage Disposal Systems, 1977) govern household and small flow sewage disposal systems in Ohio. These rules first went into effect on July 1, 1974, and were later modified, becoming effective on July 1, 1977. Chapter 3701-29 of the OAC dictates rules for the design, construction, installation, location, maintenance, and operation of household sewage disposal systems.
On December 1, 2004, the 125th Ohio General Assembly passed Sub. H.B. 231 "Household Sewage Treatment Regulation" and on May 5, 2005, enacted chapter 3718 of the Ohio Revised Code, creating authority for the Ohio Department of Health to establish standards for the proper siting, design, installation, monitoring, operation and maintenance, and abandonment of sewage treatment systems. To facilitate this process and to incorporate inputs from industry, academia, state agencies, and other stakeholders, the Ohio Department of Health established the Sewage Advisory Committee, which submitted a draft of new rules to the Public Health Council in April 2006. The Public Health Council adopted the rules in May 2006 that became effective on January 1, 2007, greatly expanding the use of different system technologies in Ohio.
Concerns relating to the cost of new and replacement systems under the new law were raised. As a result, effective July 1, 2007, the 127th Ohio General Assembly suspended the state sewage law and rescinded the sewage treatment system rules. Am. Sub. H.B. 119 authorized the Ohio Department of Health to readopt the 1977 Household Sewage Disposal Rules as statewide interim rules providing minimum standards for sewage treatment systems in Ohio.
In June 2010, Sub. S.B. 110 was passed by the Ohio Senate and House of Representatives and signed into law on June 18, 2010. The law became effective on September 17, 2010, and required that new statewide rules be drafted and adopted no sooner than January 1, 2012. Until the new rules are adopted, the current state minimum rules, as stipulated in OAC chapter 3701-29 and stricter regulations adopted by local health districts, remain in effect. The law also required the Home Sewage and Small Flow Onsite Sewage Treatment Study Commission to recommend effective options to treat sewage to guarantee public health protection with minimal economic impacts. Table 1 presents a timeline of Ohio's septic systems regulatory process.
Septic System Technologies
The statewide survey of county health departments achieved an 87.5% response rate (77 out of the 88 counties). The response rate is similar to that obtained in earlier such surveys conducted in 1986-87 (Mancl, 1990) and 1995 (Mancl, 1999). All the counties in the state permit traditional leach field systems. Use of advanced systems varies by county, however. The survey revealed that 68 counties (88%) permit the use of aerobic systems, down from 96% in 1986 (Mancl, 1990).
Sand filters are permitted in 60 counties (78%), up from 63% in 1986 (Mancl, 1990).
In Ohio, two types of mound systems are used. One is an evapotranspiration (ET) mound and the other is a Wisconsin-style treatment mound. Wisconsin-style treatment mound systems were reported to be in use in 40 counties (52%). Earlier studies reported lower usage: 21 counties (26%) in 1986 and 25 counties (31%) 1995. Both treatment mounds and ET mounds were reported in the 1986 and 1997 surveys. If ET mounds are excluded from those numbers, the use of Wisconsin-style treatment mounds has increased significantly in the last 20 years in Ohio. Table 2 lists the number of counties that permit each of these advanced treatment systems and compares the numbers to those reported in earlier studies.
The Ohio Department of Health conducted a survey of county health districts in 2011 to assess the use of linear loading and hydraulic loading rate estimates in the design of wastewater treatment systems (R. Fugitt, personal communication, August 8, 2011). Tyler (2001) designed a table to estimate the design infiltration loading and hydraulic linear loading rates for soil-based onsite wastewater systems. Sixty counties responded to the survey request, and 44 counties (73%) reported using linear and hydraulic loading as the standard for designing systems.
Because the Ohio onsite sewage disposal rules predate the development of advanced onsite wastewater treatment technologies, a mechanism was created in Sub. H.B. 231 to evaluate and recommend the use of "experimental systems" in Ohio. A Sewage Treatment System Technical Advisory Committee (TAC) was established in May 2005 under Section 3718.03 of the Ohio Revised Code. The TAC is a mechanism to recommend approval or disapproval of sewage treatment systems that differ in design and function from those authorized for use in the Ohio Administrative Code 3701-29. The TAC works in conjunction with the Ohio Department of Health and reports to the director of health. The TAC also supports research and development of innovative and cost-effective household sewage treatment system components, including conducting pilot projects to assess the effectiveness of such components.
To date, the TAC has approved septic tanks, pretreatment systems, and special devices for household wastewater treatment (Ohio Department of Health, 2012). Twenty-one pretreatment devices have been approved including two peat biofilters, one textile and one foam biofilter, two ultraviolet light systems, and 14 aerobic units. Nine special devices have been approved including sand mound systems with pressure distribution, sand bioreactors that are either time-dosed or use siphons, and drip distribution systems.
Septic System Installations
The Ohio Department of Health was directed by the Ohio legislature to prepare a comprehensive analysis on the types of alternative waste treatment systems and their costs and economic factors. Information on permits for treatment systems installed between July 1, 2007, and November 30, 2007, revealed that new household systems accounted for 70% of all systems installed, while replacement and alterations were 18% and 12% of the total, respectively. Additionally, 72% of all systems installed were septic systems with traditional leach lines, 10% were mound systems, 3% were drip irrigation systems, 6% were National Pollutant Discharge Elimination System-approved discharging systems (replacements of existing discharging systems), while the remaining 9% were other systems or systems with no information. Since advanced systems are only now beginning to be adopted at higher rates, it can be hypothesized that leach fields form an even higher proportion of the existing septic systems. Based on the information presented in Ohio Department of Health (2008), the average estimated cost of installing these systems is
* $7,250 for septic systems with leach fields,
* $19,750 for drip irrigation systems.
Approximately 25% of Ohio's households are served by some type of sewage system located on the property, with an estimated one million systems in use today. The Ohio Department of Health estimates that 480 gallons of wastewater per household are released in the environment every day, based on the assumption that sewage systems generate 120 gallons per day of wastewater per bedroom and an average home size of four bedrooms. Using the land area calculations for the design of leach fields (Mancl, 2009), mound systems (Chen & Mancl, 2004), and spray irrigation systems (Rowan, Mancl, & Caldwell, 2004) on the statewide distribution of onsite systems and the design wastewater volume for a four-bedroom home as suggested by the Ohio Department of Health, the total land area in Ohio under onsite treatment systems was estimated to be 71,183 acres, which is 0.25% of the state's area.
Seasonal saturation in the soils and the presence of shallow bedrock are two common conditions that threaten the public health (Ohio Department of Health, 2008). Mancl and Slater (2001) found that only 6.4% of Ohio's land area is suited for septic system leach fields. They have identified 215 soil series that have less than one foot of soil depth to seasonal high water tables or other limiting conditions. The Ohio Department of Health (2008) reported a septic system failure rate of 30%. This figure is higher than previous studies showing estimated failure rates of 13% 20% (Tumeo & Newland, 2009), 20%-25% (Maumee River Remedial Action Plan, 2004), and 27% (Mancl, 1990; Ohio Environmental Protection Agency, 1995). Assuming a conservative failure rate of 25%, approximately 120 million gallons of untreated or partially treated wastewater are discharged daily to surface water and groundwater. The failure of septic systems has been attributed to various causes, primarily inadequate soil quality, underdesign, age of the system (DeWalle, 1981; Mancl & Slater, 2000), and soil clogging due to failure to remove excess sludge from the septic tank (Mancl & Slater, 2000).
The primary role of regulators is issuing permits for onsite wastewater treatment systems. Often, regulators also deal with aspects of designing, installing, and operating these onsite systems. Mancl (1990) reported that Ohio regulators issued approximately 13,000 permits in 1986. Given that regulators are responsible for issuing a large number of permits each year, it becomes critical for them to be familiar with the latest technologies and regulations governing the onsite wastewater industry. To effectively educate Ohio regulators on onsite wastewater treatment, it is important to understand the different tasks performed by regulators and the skills associated with these tasks.
To determine necessary skills, knowledge, and abilities, respondents were asked to indicate three of the most common skills and practices used to accomplish daily tasks. The top three responses (n = 66) were soil-related information (30.8%), general knowledge (17.5%), and communication (16.6%). Responses stating soil evaluation, interpreting soil maps, soil identification, percolations tests, etc., were grouped under soil-related information. Skills pertaining to general knowledge included knowledge of regulations, wastewater treatment subject matter, and industry norms; common sense; and use of mathematics. Skills pertaining to communication included verbal and written communication; conflict resolution; communication among regulators, contractors, designers, and the public; and diplomacy and delivering notification of violations.
When respondents were asked to indicate areas where they lacked preparedness (n = 70), homeowner concerns (24.3%), issues involving zoning (14.3%), drainage-related issues (11.4%), and design (10%) were the most important areas indicated in the responses. Twenty percent of the respondents felt well equipped in their daily tasks. According to the regulators, areas for improvement (n = 73) included more education (31.5%), issues related to funding (23.3%), and state regulations (17.8%). Comments on education included increase in research on onsite wastewater management and education of the public, designers, contractors, and regulators. Respondents also commented on funding issues such as financial assistance for low-income households as well as state and federal money allocated to health districts to undertake system repairs and educational programs. Comments regarding the state regulations varied from support for the existing rules and the expectation of simpler rules in the future to criticism about the role of health departments in the regulatory process.
Many educational programs are available to meet regulators' educational needs, with some of them utilized more than others. Educational programs are offered by state agencies such as the Department of Health and the Department of Natural Resources, professional organizations such as the Ohio Onsite Wastewater Association and National Onsite Water Recycling Association, and The Ohio State University through its extension programs. Respondents were asked to indicate the source of their knowledge on various topics such as permitting, design and inspection of wastewater treatment systems, and site and soil evaluations as seen in Table 3. Workshops conducted by state agencies, professional organizations, and The Ohio State University Extension are the most common educational sources for regulators.
Rules regarding regulation and management of septic systems in Ohio are governed by the Ohio Administrative Code (Household Sewage Disposal Systems, 1977). Since the enactment of these rules, changes have occurred in the technology used for treatment of wastewater as well as growth patterns of urban and rural communities. The first major legislative action to update the rules was in 2004, when Sub. H.B. 231 was approved in 125th Ohio General Assembly. One major change included in Sub. H.B. 231 was the elimination of curtain drains, which were to be replaced with engineered interceptor drains, gradient drains, or not having a drain. A curtain drain, as defined in Chapter 3701-29 of the Ohio Administrative Code (Household Sewage Disposal Systems, 1977), is any subsoil drain used to prevent the entrance of groundwater into the area occupied by the household sewage disposal system. Curtain drains do not treat wastewater, however, but merely allow subsurface movement of untreated wastewater, discharging pollutants and nutrients to surface waters. When the statewide survey was conducted in 2005, 13 counties (17%) required curtain drains on all systems and 58 counties (75%) required them under certain conditions such as seasonally high or perched water tables, runoff towards septic system, and poorly drained soils. Only six counties (8%) did not require curtain drains in their jurisdiction at the time. Although the use of curtain drains has increased in the recent past (Vedachalam, Hitzhusen, & Mancl, 2012), their effectiveness in protecting groundwater quality has not been established (Dumouchelle, 2006).
The study undertaken by the Ohio Department of Health (2008) indicates that septic system failures appear to be higher than estimated earlier. The study reported the failure rate of septic systems to be around 30%, higher than the earlier documented rates that ranged from 13% to 27%. At this rate, approximately 120 million gallons of untreated or partially treated wastewater is discharged daily to surface and ground water. While failure of individual septic systems is difficult to monitor, large-scale system failures may result in enforcement action from the Ohio Environmental Protection Agency (OEPA). Records from OEPA show that during 1986-2007, over 240 communities were under enforcement or identified as having significant impacts from failing systems (Ohio Department of Health, 2008). As a result, the survey of county health departments across the state shows that the use of discharging aerobic systems has decreased over a 20-year period, while sand filters and mound treatment systems are permitted in more counties than before.
At an individual level, failing systems may result in significant costs such as negative health effects and a resulting cost of illness leading to a reduced quality of life. In addition, an individual may also incur higher maintenance and repair costs for poorly designed systems and a loss of property valuation. Vedachalam and co-authors (2012) reported that properties with septic systems sited on unsuitable soils were likely to be valued 6.2% to 6.8% lower than comparable properties on suitable soils based on a study conducted in Licking County, Ohio. Vedachalam (2011) proposed a survey instrument to measure the cost of illness from failing septic systems by interviewing homeowners on the status of their septic systems and obtaining a rough measure of the health costs due to the septic systems.
Officials in the county health departments are tasked with issuing permits and overseeing installation, design, and operation of onsite systems. A survey of regulators in Ohio highlighted needs in soil evaluation and improved communication skills. Survey respondents indicated education as an area for improvement including research on onsite wastewater management and education of public, designers, contractors, and regulators. A variety of educational programs are offered by state agencies, professional organizations, and The Ohio State University Extension. Respondents attributed their knowledge on issues related to wastewater management to workshops conducted by these agencies over more than 20 years (Mancl, 1999). These educational programs will be even more important when new rules take effect after January 2012.
Because most of Ohio's soils are not suited for traditional leach fields that require deep unsaturated soils for complete treatment of the wastewater, advanced technologies are needed to properly treat wastewater for rural homes. Even with the oldest rules in the U.S., the TAC established by state law has enabled Ohio to carefully evaluate the scientific merit of proposed technologies and introduce them into the market. Cost studies conducted by the Ohio Department of Health have found that while septic system leach fields are the least expensive wastewater treatment systems, technologies such as treatment mounds and drip irrigation systems that are capable of treating wastewater on sites with shallower soils cost less than $20,000 to install.
County health officials are tasked with issuing permits for new onsite treatment systems.
Health officials, however, often also deal with aspects of installing, designing, and operating these onsite systems. Delineation of regulatory tasks will likely avoid potential conflict of interests. Improving the competency of the regulators; strengthening research and development efforts on new and innovative sewage treatment systems; and educating contractors, designers, and the general public could be some of the outcomes expected from the regulatory transition process.
Regulators need to be trained in the permitting, design, and installation of onsite systems along with the advances in treatment technologies. The various workshops offered by state agencies, professional organizations, and The Ohio State University Extension are the primary sources of training for regulators. In light of the proposed new regulations in 2012, workshops and educational programs targeted at regulators will help the counties and local districts transition to the new rules. Pilot studies conducted in selected counties after the implementation of the proposed new rules could help analyze the impact of the regulations and the effectiveness of training programs for regulators.
Acknowledgements: Salaries and research support provided by state and federal funds appropriated to the Ohio Agricultural Research and Development Center, The Ohio State University. The participation of county health departments in the survey is acknowledged. Comments from the two anonymous reviewers and the technical editor were helpful in improving the manuscript.
Chen, C.-L., & Mancl, K. (2004). Mound systems for onsite wastewater treatment. Ohio State University Extension Bulletin, 813.
DeWalle, E (1981). Failure analysis of large septic tank systems. Journal of the Environmental Engineering Division, 107(1), 229-240.
Dillman, D.A. (1978). Mail and telephone surveys: The total design method. New York: Wiley Press.
Dumouchelle, D. (2006). Assessment of the use of selected chemical and microbiological constituents as indicators of wastewater in curtain drains from home sewage treatment systems in Medina County,
Ohio (Scientific Investigations Report 2006-5183). Reston, VA: U.S. Geological Survey. Retrieved from http://pubs.usgs.gov/sir/2006/5183/pdf/SIR_2006_5183.pdf
Hacker, E.B. (2007). Educational needs of Ohio regulators on onsite wastewater treatment systems. Unpublished master's thesis, The Ohio State University, Columbus.
Household Sewage Disposal Systems (Ohio Administrative Code), Chapter 3701-29 (1977).
Mancl, K. (1990). A survey of small sewage treatment facilities in Ohio. The Ohio Journal of Science, 90(4), 112-117.
Mancl, K. (1999). Survey of approval practices for onsite sewage treat ment systems in Ohio. The Ohio Journal of Science, 99(3), 38-43. Mancl, K. (2009). Septic tank-soil treatment systems. Ohio State University Extension Bulletin, 939.
Mancl, K., & Slater, B. (2000). Why do septic systems malfunction? Ohio State University Extension Fact Sheet, 741.
Mancl, K., & Slater, B. (2001). Suitability assessment of Ohio's soils for soil-based wastewater treatment. The Ohio Journal of Science, 101(3/4), 48-56.
Maumee River Remedial Action Plan. (2004). Maumee River area of concern stream & septic monitoring study final report. Perrysburg, OH: Author.
Ohio Department of Health. (2008). Report to the household sewage and small flow onsite sewage treatment system study commission. Columbus, OH: Author
Ohio Department of Health. (2012). Approved systems and components. Retrieved from http://www.odh.ohio.gov/odhprograms/eh/sewage/Approvedsystemscomponents/sewmore.aspx
Ohio Environmental Protection Agency. (1995). State of the environment report (Ohio Comparative Risk Project). Columbus, OH: Author.
Rowan, M., Mancl, K., & Caldwell, H. (2004). On-site sprinkler irrigation of treated wastewater in Ohio. Ohio State University Extension Bulletin, 912.
Sewage Treatment Systems (Ohio Revised Code), Chapter 3718 (2006). Tumeo, M.A., & Newland, J. (2009). Survey of home sewage disposal systems in northeast Ohio. Journal of Environmental Health, 72(2), 17-22.
Tyler, E.J. (2001). Hydraulic wastewater loading rates to soil. Pro ceedings of the Ninth Symposium on Individual and Small Commu nity Sewage Systems, 80-86. U.S. Census Bureau. (2007). American housing surveys for the United
States. Retrieved from http://www.census.gov/housing/ahs/ U.S. Environmental Protection Agency. (1996a). National water quality inventory report to congress (Report No. EPA 841-R-97 008). Washington, DC: Author.
U.S. Environmental Protection Agency. (1996b). Clean water needs survey report to Congress. Washington, DC: Author.
U.S. Environmental Protection Agency. (1997). Response to Congress on use of decentralized wastewater treatment systems (Report No. EPA 832-R-97-001b). Washington, DC: Author.
U.S. Environmental Protection Agency. (2000). Draft EPA guidelines for management of onsite/decentralized wastewater systems. Washington, DC: Author.
U.S. Environmental Protection Agency. (2008). Septic systems fact sheet (EPA Doc. No. 832-F-08-057). Washington, DC: Author.
Vedachalam, S. (2011). Attitudinal, economic and technological approaches to wastewater management in rural Ohio. Unpublished doctoral dissertation, The Ohio State University, Columbus.
Vedachalam, S., Hitzhusen, F.J., & Mancl, K. (2012). Economic analysis of poorly sited septic systems: A hedonic pricing approach. Journal of Environmental Planning and Management. Retrieved from http://www.tandfonline.com/doi/full/10.1080/09640568.2012.673864
Corresponding Author: Sridhar Vedachalam, Postdoctoral Associate, New York State Water Resources Institute, Cornell University, 1103 Bradfield Hall, Ithaca, NY 14853. E-mail: email@example.com.
Sridhar Vedachalam, PhD
Eli Hacker, MS
Karen Mancl, PhD
The Ohio State University
TABLE 1 Timeline of Ohio's Septic Systems Regulatory Process Date Rule or Regulatory Agency July 1, 1974 Chapter 63701-29 of the Ohio Administrative Code December 1, 2004 Sub. H.B. 231 May 5, 2005 Chapter 3718 of the Ohio Revised Code April 2005 Sewage Advisory Committee May 6, 2005 Sewage Treatment System Technical Advisory Committee January 1, 2007 Public Health Council July 1, 2007 Am. Sub. H.B. 119 July 1, 2009 Home Sewage and Small Flow Onsite Sewage Treatment System Study Commission June 18, 2010 Sub S.B. 110 Date Description July 1, 1974 Governs household and small flow sewage treatment in Ohio. Later modified with effect from July 1, 1977. December 1, 2004 125th Ohio General Assembly passed a bill later signed by the governor that provided for comprehensive regulation of sewage systems in Ohio. May 5, 2005 A result of Sub H.B. 231, this rule created authority for the Ohio Department of Health to establish standards for the proper siting, design, installation, monitoring, operation and maintenance, and abandonment of sewage treatment systems. April 2005 The Ohio Department of Health created this committee composed of various stakeholders to identify decision points and draft rules, which were accepted by the Public Health Council in May 2006. May 6, 2005 Chapter 3718.03 of the Ohio Revised Code created this committee to recommend approval or disapproval of sewage treatment systems that differ in design and function from those authorized for use in the Ohio Administrative Code 3701-29. January 1, 2007 After minor revisions in October 2006, the Public Health Council adopted rules with an effective date of January 1, 2007, greatly expanding the use of different system technologies in Ohio. July 1, 2007 With effect from July 1, 2007, the 127th Ohio General Assembly suspended the state sewage law and the 1977 rules were readopted. July 1, 2009 As directed by Am. Sub. H.B. 119, the commission was required to recommend effective options to treat sewage to guarantee public health protection with minimal economic impacts. June 18, 2010 Signed by the governor after passing the Ohio Senate and House, this law required new statewide rules to be adopted no sooner than January 1, 2012. TABLE 2 Alternative Treatment Systems Permitted by Ohio Counties Treatment System Permitted in Ohio Counties 1986 1997 2005 Aerobic system 79 (96%) - 66 (86%) Sand filter 52 (63%) - 60 (78%) Mound 21 (26%) 25 (31%) 40 (52%) Note. The 2005 numbers were collected with a statewide survey. The corresponding numbers for 1986 and 1997 were obtained from Mancl (1990) and Mancl (1999), respectively. TABLE 3 Ohio Regulator Knowledge About Wastewater Issues Gained From Various Sources The Ohio State Professional State Formal Agency Organization University Coursework Workshops Workshops Extension Topic % % % Workshops % Permitting 5.8 23.5 21.9 21.6 Design 4.6 21.5 20.5 20.5 Inspection 3.1 22.3 24.4 18.1 Site and soil 5.5 22.8 22.5 17.3 evaluation Coworker Knowledge Self-Taught Other Topic % % % Permitting 12.3 12.6 2.3 Design 14.9 12.8 5.1 Inspection 14.6 13.6 3.8 Site and soil 13.5 11.4 6.9 evaluation…